In what is expected to be a fierce discussion, Argentina’s Senate is scheduled to vote Wednesday on a bill allowing gay people to wed. The proposed law has increased frictions between the Roman Catholic Church and the government of President Cristina Fernández de Kirchner, which is pushing the bill.

The war of words continued on Tuesday as church leaders staged large protests around the country against the proposed law. On Sunday, Cardinal Jorge Bergoglio, the archbishop of Buenos Aires, had declared it a “destructive attack on God’s plan.”

Mrs. Kirchner harshly criticized church leaders on Monday, saying that their discourse on the issue resembled “the times of the Crusades” and that they failed to acknowledge how socially liberal Argentina had become.

“They are portraying this as a religious moral issue and as a threat to ‘the natural order,’ when what we are really doing is looking at a reality that is already there,” the president said from Beijing. “It would be a terrible distortion of democracy if they denied minorities their rights.”

Gay rights advocates said Mrs. Kirchner and her husband, former President Néstor Kirchner, are responding to polls showing that nearly 70 percent of Argentines support giving gay people the same marital rights as heterosexuals.

Some political analysts see the issue as a political maneuver for the Kirchners to maintain their dynasty in Argentina. Mr. Kirchner, now a congressman, has been spearheading the gay marriage bill to regain the limelight before the 2011 elections, when he is widely expected to try to run for president again, said Carlos Germano, a political analyst in Buenos Aires.

Mr. Kirchner “is trying to notch up a victory to regain his political leadership and his management of the political agenda,” especially as opposition parties show their first signs of creating a united front to challenge the Kirchners, Mr. Germano said.

But it is a political gamble that could split Mr. Kirchner’s power base and cost him leadership of the Peronist Party, analysts said.

Even so, the Kirchners seem intent on making history. If the Senate votes for the bill, approved by the lower house of Congress in May, Argentina would become the first country in Latin America to allow same-sex marriages affording all rights of heterosexual unions. Mexico City became the first jurisdiction in Latin America to legalize same-sex marriages in December. Two other countries in the region, Uruguay and Colombia, allow civil unions for gay couples.

Uruguay’s law, passed in late 2007, allows couples of any sex to enter into a civil union after they live together for at least five years, entitling them to most of the benefits of married couples, including Social Security entitlements and inheritance rights.

Argentina’s government seeks to go further. Its bill would grant inheritance and adoption rights and view same-sex couples as equal under the law.

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Some senators who oppose the proposal, based on Spain’s same-sex marriage law, see it as technically flawed. The law would allow gay couples to adopt children without the three-year waiting period that exists for heterosexual couples under 30, who must prove they cannot procreate, said Sonia Escudero, a senator who plans to vote against the bill.

Ms. Escudero is among those senators pushing instead for a law to codify civil unions, which are already allowed in some Argentine cities and provinces, that would avoid what she called the legal “chaos” of granting same-sex couples adoption rights.

Mrs. Kirchner and her supporters have called that approach unconstitutional.

Civil union “doesn’t respect equality,” said José María Di Bello, deputy director at the Red Cross in Buenos Aires. “We want the same rights with the same names, not to be considered second-class citizens.”

Mr. Di Bello helped ignite the discussion over a broader same-sex marriage law after he married Alex Freyre, the executive director of the Buenos Aires AIDS Foundation, in December in a civil ceremony in Tierra del Fuego Province. The marriage went forward with the help of a supportive governor, who ordered local officials to register it.

Since then, 100 Argentine couples have petitioned through gay activist associations for help in marrying, Mr. Di Bello said. A lesbian couple, the first to seek marital rights, is the subject of a pending Supreme Court case.

While Argentina has become more socially liberal than many of its neighbors, the Catholic Church still holds substantial sway here. For months, church leaders have sponsored protests throughout the country. Argentina’s Independence Day celebrations on Friday in the city of Tucumán were marked by sharp exchanges between Mrs. Kirchner and the archbishop there.

The Kirchners risk dividing their own supporters with the gay marriage bill, which has more support in Buenos Aires than in rural provinces. Mr. Kirchner could win over voters in Buenos Aires, where a majority of residents dislike him, while losing votes in the provinces, political analysts said.

Even those who support the law criticized its timing, saying the Kirchners could have pushed the bill when they had a majority in both houses of Congress, before March.

Mr. Kirchner “is doing this to build power and to generate a fissure in society to gain votes,” said Luis Juez, a senator from Córdoba from the opposition Civic Front party, who said he planned, nevertheless, to vote for the bill.

“He is not doing it for human rights and the rights of minorities. This is a totally arbitrary political operation,” he said.

Charles Newbery contributed reporting.

A version of this article appears in print on July 14, 2010, on Page A11 of the New York edition with the headline: Argentina Senate to Vote On Same-Sex Marriage Bill. Order Reprints|Today's Paper|Subscribe